In a touch screen technique, a capacitive touch screen is advantageous in terms of a long lifespan, a high transmittance, an ability of supporting a multi-point touch, etc, as compared with a resistive touch screen. Also, the capacitive touch screen has a perfect inhibitory effect on noises and an earth parasitic capacitance. Therefore the capacitive touch screen has been popular in manufacture of touch screen. Further, an In-Cell capacitive touch screen may not only thin a thickness of a display module but also reduce a manufacture cost of the touch screen greatly by embedding touch electrodes inside a display screen in the display module, and is favored by many panel producers.
A touch detection principle of the capacitive touch screen is as follows: touch driving electrodes and touch sensing electrodes which are arranged as being intersected with each other horizontally and vertically are formed in the touch screen, capacitors are formed at intersections so as to from a capacitor array, then a touch scan signal is applied to respective lines of touch driving electrodes sequentially, and output signals from the touch sensing electrodes corresponding to each line of touch driving electrodes are detected sequentially, so that capacitance variation in the capacitor array may be detected and a touch position may be judged.
Because of the requirement for adding the touch driving electrodes and the touch sensing electrodes on the display screen, a frame width of an entire display module may increases. In addition, since a display time for one frame of image includes a touch detection period and a charging and displaying period of the pixel unit, a charging time for a pixel unit is shortened extremely, which increases a design difficulty of the pixel unit.